Measuring ketosis with an Arduino

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A bit of biology and nutrition before we roll into this: Ketosis is when your body runs on fat reserves instead of carbohydrates. This is the basis of diets such as Atkins, and despite the connotations of eating hamburger patties and butter, you can actually lose weight on these diets. One problem with a keto diet is the difficulty of measure how many ketones your liver is processing; this can be done with a urine sample, but being able to measure small amounts of acetone in your breath would be the ideal way to measure ketosis. [Jens] came up with a device that does just that. It’s called Ketosense, and it will tell you how well your keto diet is doing by just having you blow into a sensor.

[Jens]‘ device consists of an Arduino, LCD display, and two sensors – one for acetone, and another for temperature and humidity. By carefully calibrating a TGS822 sensor, [Jens] was able to measure the acetone content of an exhaled breath along with temperature and pressure. This gave him a reading in parts per million, and with a short bit of math was able to convert that into something that made sense when talking about ketosis, mmol/l.

Without access to a lab that can measure blood ketone levels, it’s difficult to say if [Jens] device really works as intended. If he were to find his way into a lab, though, it would be possible to correlate his sensor’s values with blood ketone results and improve the accuracy of his sensor.

Gas sensor suite built with Gadgeteer modules

gadgeteer-gas-sensor-suite

[Blake] just finished a gas sensor suite built from Gadgeteer parts. The three sensors are the cylindrical towers along the left hand side of the assembly. The one at the top (with the orange ring) is an alcohol sensor. The middle one senses ammonia and the lower sensor measures air quality. Also rolled into the mix are temperature and humidity sensors.

You can collect a lot of data with this type of setup. To keep it organized [Blake] used the ThingSpeak interface. Using the NIC in the upper right he uploads the measurements for real-time graphing. The setup is explained in detail in the video after the break, including a test with some cleaning ammonia.

We haven’t tried out the Gadgeteer system for ourselves yet. But you’ve got to admit that the ribbon cable connector system the family of parts uses really helps to keep a rather complicated setup like this one nice and tidy.

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Bathroom fan that switches itself on when it gets steamy or smelly

At first we thought that [Brandon Dunson] was writing in to tell us he’s too lazy to fix his bathroom fan. What he really meant is that simply replacing the unit isn’t nearly enough fun. Instead, he developed his own bathroom fan trigger based on stinky or humid air conditions. He didn’t publish a post about the project but we’ve got his entire gallery of build images after the break.

The initial inspiration for the project came from a twitter-connected fart sensing office chair. Hiding behind the character display you can see the MQ-4 methane gas sensor which he picked up for the project. But since there’s also a shower in the bathroom he included a humidity sensor with the project. Both are monitored by an ATmega328 which averages 10 readings from each sensor before comparing the data with a set threshold. If the sensors read above this level a relay turns on the bathroom fan.

Don’t be confused by the small DC fans seen above; [Brandon] is still using a proper exhaust fan. These are just used to help circulate the air around the sensors so that low-hanging smells will still trigger the system. This has got to be the perfect thing for a heavily used restroom.

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DIY Breathalyzer may be the hit of the party

Okay, this may not be saving any lives, but it makes for a fun novelty at your next rager. Most Breathalyzers aim to keep you from driving when you’ve had too many. The Squidalyzer encourages party-goers to drink more and more by treating a high blood-alcohol-content with great fanfare. An Arduino, a gas sensor, and Processing all come together for this hack. A television interface tells you when to blow into a cup which houses the sensor, and gives a reading of what it measures. Blow higher than the last guy and you’ll break the record. Watch the demo after the break to see the fun [Geoff] had with it. And remember, friends don’t let friends solder drunk.

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